The main objective of this study is to examine the effects of intravenous anesthetics on general and regional hemodynamics in both normal and pathologic cardiovascular states. It is assumed that intravenous agents are relatively benign in their hemodynamic effects (58,62,121) and therefore are safe in subjects with minimal cardiovascular reserve (68,74,91). Preliminary data indicate that this assumption is not entirely true. Morphine decreases intestinal and skeletal muscle blood flow and merperidine decreases intestinal flow. In addition, others have shown that morphine constricts the coronary circulation (114). It is also noteworthy in our preliminary studies, that both morphine and meperidine increase renal blood flow. The drugs to be tested are thiopental, diazepam, ketamine, meperidine, morphine and fentanyl. The regional hemodynamic effects of these drugs on the cononary, renal, intestinal, hepatic and skeletal muscle vascular beds will be examined. Appropriate catheters will be placed and either electromagnetic or Doppler ultrasonic flow probes implanted in dogs under general anesthesia 2-3 weeks prior to the studies. Experiments will be performed on intact, conscious animals whose cardiovascular systems are in either a normal or a pathologic state. Pathologic conditions will be established in two ways; hypovolemia induced by acute hemorrhage and chronic left-sided heart failure accomplished by an outflow occlusion technique. Aortic and carotid baroreceptor ablations and appropriate autonomic blocking agents will be employed to selectively interrupt the afferent and efferent limbs, respectively, of the neurovascular control loop to explore the mechanisms of any observed changes.